Alaska Extended Forecast Discussion NWS Weather Prediction Center College Park MD 702 PM EDT Mon May 24 2021 Valid 12Z Fri May 28 2021 - 12Z Tue Jun 01 2021 ...Overview and model guidance... The overall pattern across Alaska for the medium range period will feature a large scale upper level low that will move south of the Aleutians this weekend, while a second cutoff low drifts westward across the mainland and into the Bering Sea. The two systems should begin to interact with each other by late period as upper level ridging builds back in across central and northern Alaska. At the surface this translates to a frontal boundary draped across southern Alaska while a closed low and a series of frontal boundaries affects the Aleutians and southern Coast locations. The latest suite of guidance shows above average agreement on the overall large scale pattern, but some uncertainty with regards to details of individual perturbations around the Aleutians low and also how the two lows may interact late in the period. WPC favors a blend heavily weighted towards the GFS/ECMWF through day 6. The CMC was excluded from the blend today due to differences in placement and movement of the cutoff mainland low (bringing it more south than west). After day 6, started to increase the ECENS/GEFS means a little bit to help mitigate the harder to resolve details. However, did maintain more than usual weighting of the deterministic solutions through day 8 to help maintain definition to the cutoff low (which gets quickly washed out by the means). ...Weather/Threats Highlights... The low pressure center and associated fronts into the Aleutians should bring several days of unsettled weather (winds and rain) to areas from the eastern Aleutians to the Panhandle. Models show anomalous moisture being streamed northward into the region, likely to result in periods of moderate to heavy precipitation. There remains some uncertainty regarding the details, but at this time, the best signal for highest totals during the five-day period exists from the Kenai Peninsula to the northern Panhandle where some places could see several inches of rain from this weekend into early next week. The cutoff low through eastern and central Alaska will bring temperatures modestly below normal to start the period on Friday, but should steadily rebound back towards or even above normal as the low exits into the Bering Sea this coming weekend. By early next week, temperatures should be near or above normal from western regions through the central part of the state as upper level ridging builds aloft. Meanwhile, expect below normal temperatures through the entire period from the Aleutians to the Panhandle and parts of Southern Alaska underneath of cloudy and rainy skies. Santorelli Additional 3-7 Day Hazard information can be found on the WPC medium range hazards chart at: https://www.wpc.ncep.noaa.gov/threats/threats.php Hazards: - Heavy rain across portions of the Alaska Panhandle and mainland Alaska, Fri-Sun, May 28-May 30 WPC medium range Alaskan products including 500mb, surface fronts/pressures progs and sensible weather grids can also be found at: https://www.wpc.ncep.noaa.gov/alaska/ak_5dayfcst500_wbg.gif https://www.wpc.ncep.noaa.gov/alaska/akmedr.shtml https://www.wpc.ncep.noaa.gov/alaska/ak_5km_gridsbody.html